Maternal or Paternal Antibiotics? Intergenerational Transmission and Reproductive Toxicity in Zebrafish.

Despite the known direct toxicity of various antibiotics to aquatic organisms, the potential chronic impact through intergenerational transmission on reproduction remains elusive. Here, we exposed zebrafish to a mixture of 15 commonly consumed antibiotics at environmentally relevant concentrations (1 and 100 µg L-1) with a cross-mating design. A high accumulation of antibiotics was detected in the ovary (up to 904.58 ng g-1) and testis (up to 1704.49 ng g-1) of F0 fish. The transmission of antibiotics from the F0 generation to the subsequent generation (F1 offspring) was confirmed with a transmission rate (ki) ranging from 0.11 to 2.32. The maternal transfer of antibiotics was significantly higher, relative to paternal transfer, due to a greater role of transmission through ovarian enrichment and oviposition compared to testis enrichment. There were similar impairments in reproductive and developmental indexes on F1 eggs found following both female and male parental exposure. Almost all antibiotics were eliminated in F2 eggs in comparison to F1 eggs. However, there were still reproductive and developmental toxic responses observed in F2 fish, suggesting that antibiotic concentration levels were not the only criterion for evaluating the toxic effects for each generation. These findings unveil the intergenerational transmission mechanism of antibiotics in fish models and underscore their potential and lasting impact in aquatic environments.

Poly- and Perfluoroalkyl Substances Induce Immunotoxicity via the TLR Pathway in Zebrafish: Links to Carbon Chain Length.

Previous studies have reported the immunotoxicity of per- and polyfluoroalkyl substances (PFASs), but it remains a significant challenge to assess over 10,000 distinct PFASs registered in the distributed structure-searchable toxicity (DSSTox) database. We aim to reveal the mechanisms of immunotoxicity of different PFASs and hypothesize that PFAS immunotoxicity is dependent on the carbon chain length. Perfluorobutanesulfonic acid (PFBA), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) representing different carbon chain lengths (4-9) at environmentally relevant levels strongly reduced the host's antibacterial ability during the zebrafish's early-life stage. Innate and adaptive immunities were both suppressed after PFAS exposures, exhibiting a significant induction of macrophages and neutrophils and expression of immune-related genes and indicators. Interestingly, the PFAS-induced immunotoxic responses were positively correlated to the carbon chain length. Moreover, PFASs activated downstream genes of the toll-like receptor (TLR), uncovering a seminal role of TLR in PFAS immunomodulatory effects. Myeloid differentiation factor 88 (MyD88) morpholino knock-down experiments and MyD88 inhibitors alleviated the immunotoxicity of PFASs. Overall, the comparative results demonstrate differences in the immunotoxic responses of PFASs due to carbon chain length in zebrafish, providing new insights into the prediction and classification of PFASs mode of toxic action based on carbon chain length.

Perfluorononanoic Acid Induces Neurotoxicity via Synaptogenesis Signaling in Zebrafish.

Perfluorononanoic acid (PFNA), commonly used as an alternative polyfluorinated compound (PFC) of perfluorooctanoic acid (PFOA), has been widely detected in the aquatic environment. Previous ecotoxicological and epidemiological results suggested that some neurobehavioral effects were associated with PFC exposure; however, the ecological impacts and underlying neurotoxicity mechanisms remain unclear, particularly in aquatic organisms during sensitive, early developmental stages. In this study, zebrafish embryos were exposed to environmentally relevant concentrations of PFNA for 120 h, and the neurological effects of PFNA were comprehensively assessed using transcriptional, biochemical, morphological, and behavioral assays. RNA sequencing and advanced bioinformatics analyses predicted and characterized the key biological processes and pathways affected by PFNA exposure, which included the synaptogenesis signaling pathway, neurotransmitter synapse, and CREB signaling in neurons. Neurotransmitter levels (acetylcholine, glutamate, 5-hydroxytryptamine, γ-aminobutyric acid, dopamine, and noradrenaline) were significantly decreased in zebrafish larvae, and the Tg(gad67:GFP) transgenic line revealed a decreased number of GABAergic neurons in PFNA-treated larvae. Moreover, the swimming distance, rotation frequency, and activity degree were also significantly affected by PFNA, linking molecular-level changes to behavioral consequences.

Online TG-FTIR-MS analysis of the catalytic pyrolysis of polyethylene and polyvinyl chloride microplastics.

Microplastics (MPs) are frequently detected in urban waters, which would pose a threat to human health through the food chain. Thus, efficient approaches to the elimination of MPs are urgently required. Pyrolysis is a powerful technique for the potential treatment of MPs. The online thermogravimetry-Fourier transform infrared reflection-Mass spectrometry (TG-FTIR-MS) is applied for tracking the pyrolysis process of representative polyethylene (PE) and polyvinyl chloride (PVC) MPs in urban waters, together with or without the FeAlOx catalyst. TG could quantitatively determine the decomposition behavior and kinetics of MPs while FTIR and MS spectra would be capable of characterizing the pyrolysis products. The results revealed that FeAlOx is an excellent carbon support, and the deposited carbon can be gasified to CO at higher pyrolysis temperatures. Moreover, more aromatic compounds were generated from the pyrolysis of PE MPs with the catalyzation of FeAlOx. Large quantities of benzene were also produced in the PVC MPs pyrolysis with or without FeAlOx. Also, FeAlOx largely decreased the concentrations of chlorine-containing compounds in the liquid products of PVC MPs pyrolysis. This study provides a efficient technique for the online observation of the MPs' catalytic pyrolysis process, which would guide future upcycling of MPs into value-added products.

Parental transfer of an antibiotic mixture induces cardiotoxicity in early life-stage zebrafish: A cross-generational study.

Antibiotic residues in the aquatic environment have been shown to induce significant adverse effects on the early-life stage development of aquatic organisms, though the underlying molecular mechanisms of these effects have not been well characterized. In this study, we performed global mRNA-miRNA sequencing, canonical pathway analyses, morphological, physiological, immunohistochemical, and behavioral analyses to comprehensively assess the cross-generational cardiotoxicity and mechanisms of antibiotic mixtures in zebrafish. Following parental treatment to 1 and 100 µg/L antibiotic mixtures (15 of the most commonly detected antibiotics) for 150 days, all 15 assessed antibiotics were detected in the F1 eggs, indicating the cross-generational transfer of antibiotics. Global mRNA-miRNA sequencing functional analysis predicted cardiotoxicity in the F1 generation by using the F1 whole fish. Consistent with canonical pathway analyses, significant cardiotoxicity was observed in F1 larvae, as well as the apoptosis of cardiac cells. Furthermore, let-7a-5p regulated the cardiac hypertrophy signaling pathway, suggesting mechanisms of miRNA of let-7 family mediating cross-generational cardiotoxicity of antibiotics in zebrafish. This study lays some groundwork for developing interventions to prevent parental exposure to environmental pollutants such as antibiotics from adversely affecting offspring development.

Translocation, bioaccumulation, and distribution of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in plants.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent in the environment and have been detected in a variety of plants such as vegetables, cereals, and fruits. Increasing evidence shows that plants are at a risk of being adversely affected by PFASs. This review concludes that PFASs are predominantly absorbed by roots from sources in the soil; besides, the review also discusses several factors such as soil properties and the species of PFASs and plants. In addition, following uptake by root, long-chain PFASs (C ≥ 7 for PFCA and C ≥ 6 for PFSA) were preferentially retained within the root, whereas the short-chain PFASs were distributed across tissues above the ground - according to the studies. The bioaccumulation potential of PFASs within various plant structures are further expressed by calculating bioaccumulation factor (BAF) across various plant species. The results show that PFASs have a wide range of BAF values within root tissue, followed by straw, and then grain. Furthermore, owing to its high water solubility than other PFASs, PFOA is the predominant compound accumulated in both the soil itself and within the plant tissues. Among different plant groups, the potential BAF values rank from highest to lowest as follows: leaf vegetables > root vegetables > flower vegetables > shoot vegetables. Several PFAS groups such as PFOA, PFBA, and PFOS, may have an increased public health risk based on the daily intake rate (ID). Finally, future research is suggested on the possible PFASs degradation occurring in plant tissues and the explanations at genetic-level for the metabolite changes that occur under PFASs stress.

Antibiotic Chlortetracycline Causes Transgenerational Immunosuppression via NF-κB.

The extensive and increasing global use of antibiotics results in the ubiquitous presence of antibiotics in the environment, which has made them "pseudo persistent organic contaminants." Despite numerous studies showing wide adverse effects of antibiotics on organisms, the chronic environmental risk of their exposure is unknown, and the molecular and cellular mechanisms of antibiotic toxicity remain unclear. Here, we systematically quantified transgenerational immune disturbances after chronic parental exposure to environmental levels of a common antibiotic, chlortetracycline (CTC), using zebrafish as a model. CTC strongly reduced the antibacterial activities of fish offspring by transgenerational immunosuppression. Both innate and adaptive immunities of the offspring were suppressed, showing significant perturbation of macrophages and neutrophils, expression of immune-related genes, and other immune functions. Moreover, these CTC-induced immune effects were either prevented or alleviated by the supplementation with PDTC, an antagonist of nuclear factor-κB (NF-κB), uncovering a seminal role of NF-κB in CTC immunotoxicity. Our results provide the evidence in fish that CTC at environmentally relevant concentrations can be transmitted over multiple generations and weaken the immune defense of offspring, raising concerns on the population hazards and ecological risk of antibiotics in the natural environment.

Occurrence and distribution of antibiotics in groundwater, surface water, and sediment in Xiong'an New Area, China, and their relationship with antibiotic resistance genes.

The emergence and pollution of antibiotics in surface water in various regions have drawn widespread concern because of the harm to aquatic ecosystems and human health. In this study, we aim to first investigate contamination and ecological risks of 39 antibiotics in Xiong'an New Area (XANA), China, and then illuminate relative abundances of antibiotic resistance genes (ARGs) and their correlations with antibiotics. The sum of antibiotic concentrations in the water circulation system, including surface water, groundwater, and sediment was 12.71-260.56 ng/L, ND-196.12 ng/L, and 38.03-406.31 ng/g, respectively. In surface water and sediment, cephalosporins and quinolones were the primary antibiotics, accounting for 45% and 16% of the total antibiotic concentrations in surface water and for 62% and 32% of the total antibiotic concentrations in sediment; this suggests a significant interaction between the two media. The antibiotic concentration was the highest in shallow groundwater at depths of <50 m (mean concentration of 79.22 ± 56.46 ng/L), indicating that surface water was a possible source of antibiotic contamination in groundwater. AMX presented the highest risk in both surface and groundwater and should be controlled as a priority. Moreover, the selection pressure of antibiotics on ARGs was discovered in the sediment in XANA, because the enrichment of sulA was significantly correlated with spiramycin and lincomycin and the enrichment of blaOXA-1 was significantly correlated with roxithromycin, ciprofloxacin, ofloxacin, and sulfapyridine. Thus, our investigation revealed potential antibiotic contamination in multiple environmental media in XANA, which should be addressed to prevent more serious pollution.

PFAS and their substitutes in groundwater: Occurrence, transformation and remediation.

Poly- and perfluoroalkyl substances (PFAS) are increasingly investigated due to their global occurrence and potential human health risk. The ban on PFOA and PFOS has led to the use of novel substitutes such as GenX, F-53B and OBS. This paper reviews the studies on the occurrence, transformation and remediation of major PFAS i.e. PFOA, PFNA, PFBA, PFOS, PFHxS, PFBS and the three substitutes in groundwater. The data indicated that PFOA, PFBA, PFOS and PFBS were present at high concentrations up to 21,200 ng L-1 while GenX and F-53B were found up to 30,000 ng L-1 and 0.18-0.59 ng L-1, respectively. PFAS in groundwater are from direct sources e.g. surface water and soil. PFAS remediation methods based on membrane, redox, sorption, electrochemical and photocatalysis are analyzed. Overall, photocatalysis is considered to be an ideal technology with low cost and high degradation efficacy for PFAS removal. Photocatalysis could be combined with electrochemical or membrane filtration to become more advantageous. GenX, F-53B and OBS in groundwater treatment by UV/sulfite system and electrochemical oxidation proved effective. The review identified gaps such as the immobilization and recycling of materials in groundwater treatment, and recommended visible light photocatalysis for future studies.

Determination of OCPs, OPPs, and 21 SVOCs in water and sediment samples in five rivers of Shenzhen, China, during the period of 2017 and 2018.

One hundred two semivolatile organic compounds (SVOCs), including 20 organochlorine pesticides (OCPs) and 12 organophosphorus pesticides (OPPs), were determined in the main rivers of Shenzhen, China. As a result, p,p'-dichlorodiphenyldichloroethane (DDD), aldrin, and benzoepin sulfate were the main OCPs detected in surface water, and p,p'-DDD, heptachlor, and endrin aldehyde were the main compounds in sediment. In addition, diazinon was the most frequent OPP detected in both water and sediment. At most sites, SVOCs were at similar concentration levels in 2017 and 2018. Compared with other areas, diazinon and malathion had comparative high concentrations in Maozhou River in this study. Analyzed from the SVOCs concentrations in water and sediment, p,p'-DDD was from the quick degradation of p,p'-dichlorodiphenyltrichloroethane (DDT), and no recent DDT was input around the investigated area. Besides, the interrelationships among these pollutants were calculated, revealing that OPPs were mainly from the chronically cumulative content, rather than the directly transferring from surface water to sediment. According to the risk assessment, the occurrence of p,p'-DDD and p,p'-DDT affected the aquatic community. All in all, further investigations on the occurrence and source of these pollutants are still needed to avoid the potential risk for human beings living around the contaminated environment.

The comparative toxicities of BPA, BPB, BPS, BPF, and BPAF on the reproductive neuroendocrine system of zebrafish embryos and its mechanisms.

Bisphenol A (BPA) is a well-known endocrine disruptor that has elicited great concern because of its potential toxic effects in organisms. In this study, the effects of BPA and several BPA structural analogs, including BPB, BPS, BPF, and BPAF, on the reproductive neuroendocrine system were evaluated during zebrafish embryonic and larval development. Our results showed that the numbers of gonadotropin-releasing hormone 3 neurons in zebrafish embryos increased after 100 µg/L BPA analog treatment, and exposure to BPA or its analogs at 1 or 100 µg/L increased the expression of reproductive neuroendocrine-related genes and the levels of typical hormones such as LH, FSH, E2, and GH. Moreover, the effects were associated with increases in the activities of erα, erß, and cyp19a genes. The respective estrogen receptors (ER) and aromatase (AROM) antagonists significantly attenuated the stimulation of lhß, fshß, LH, and FSH expression, thereby proving that BPA analogs affect the reproductive neuroendocrine system via ERs and AROM pathway. Furthermore, we observed that the reproductive neuroendocrine toxicity of BPAF was more similar to that of BPA. This was the first study to comparatively explore the reproductive neuroendocrine toxicities of bisphenols in aquatic organism.

Per- and polyfluoroalkyl substances in soil and sediments: Occurrence, fate, remediation and future outlook.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are contaminants of great concern due to their wide-spread occurrence and persistence in the environments (i.e., in water, soil and sediment) and potential toxicology even at very low concentration. The main focus of this review is on the PFASs in soil and sediments. More specifically, this review systematically examines the occurrence and toxicological effects with associated risks, fate (i.e., PFASs adsorption by soil and sediment, transportation and transformation, and bioaccumulation), and remediation practices of PFASs in soil and sediment. Various models and equations such as fugacity-based multimedia fate and hydrodynamic models are used to study the fate, transport, and transformation of PFASs. Among different remediation practices, sorption is the dominant process for the removal of PFASs from soil and sediments. Results also indicate that PFASs adsorption onto activated carbon decrease with the increase of carbon chain length in the PFASs. The longer-chain PFASs have larger partition coefficient values than shorter-chained PFASs. Sorption of PFASs to soil and sediments are mainly governed by different electrostatic interactions, hydrogen bonds formation, hydrophobic interactions, organic content in soil and sediments, and ligand exchange. Other technology such as thermal treatment might be potential in the removal of PAFSs, but need further study to elucidate a conclusion. Finally, the associated challenges and future outlook have been included.

Seasonal variation of antibiotics in surface water of Pudong New Area of Shanghai, China and the occurrence in typical wastewater sources.

The occurrence of 26 antibiotics from three groups of Sulfonamides, Quinolones and Macrolides were investigated in the surface water of Pudong New Area, Shanghai in March (dry season) and June (wet season). As a result, the detection rates of the three groups were 20%, 81% and 56% (n = 10) with the concentration range of not detected-9.73 ng L-1, 30-344 ng L-1, and 14-107 ng L-1, respectively. Comparably, during wet season, the detection rates were 20%, 56% and 25% with the range of ND-14 ng L-1, 32-92 ng L-1, and ND-22 ng L-1, respectively. This indicates higher concentrations in dry season than that in wet season, which was attributed to the water dilution and weaker self-purification of the river during dry season. In addition, significant correlations were observed between SMA and most of Quinolones during dry season, and Quinolones and Macrolides during wet season, due to the similar sources. Considering for the typical wastewater sources in the investigated area, Quinolones were identified to be the most significant group in the aquiculture water. Furthermore, pharmaceutical manufacturing factory (PMF) and sewage treatment plant (STP) should be the serious point source pollution as the concentration in their effluents could range from ng L-1 to mg L-1. The occurrence and fate of antibiotics in the aquatic system of Pudong New Area need to be paid more attention to prevent the potential risk for human beings in the future study.

Improved photocatalysis of perfluorooctanoic acid in water and wastewater by Ga2O3/UV system assisted by peroxymonosulfate.

Perfluorooctanoic acid (PFOA) has attracted considerable attention worldwide due to its widespread occurrence and environmental impacts. This research focused on the photocatalytic process for the treatment of PFOA in water and wastewater. Gallium oxide (Ga2O3) and peroxymonosulfate (PMS) were mixed directly in PFOA solution, which was irradiated under different light sources. The treatment system showed excellent performance that 100% PFOA was degraded within 90 min and 60 min under 254 nm and 185 nm UV irradiation, respectively. Moreover, the degradation efficacy was unaffected by initial PFOA concentration from 50 ng L-1 to 50 mg L-1. Acidic solution (pH 3) improved the degradation process. The quantum yield in the PMS/Ga2O3 system under UV light (254 nm) was estimated to be 0.009 mol E-1. Scavengers such as tert-butanol (t-BuOH), disodium ethylenediaminetetraacetate (EDTA-Na2) and benzoquinone (BQ) were added into PFOA solution to prove that sulfate radicals (SO4•-), superoxide radical (O2•-) and photogenerated electrons (e-) were the main active species with strong redox ability for PFOA degradation in PMS/Ga2O3/UV system. Combined with the intermediates analysis, PFOA was degraded stepwise from long chain compound to shorter chain intermediates. In addition, PFOA in real wastewater exhibited similar degradation efficiency, together with 75-85% TOC removal by Ga2O3/PMS under 254 nm UV irradiation. Therefore, Ga2O3/PMS system was highly effective for PFOA photodegradation under UV irradiation, which has potential to be applied for the perfluoroalkyl substances (PFAS) treatment in water and wastewater.

Visible and UV photocatalysis of aqueous perfluorooctanoic acid by TiO2 and peroxymonosulfate: Process kinetics and mechanistic insights.

The global occurrence and adverse environmental impacts of perfluorooctanoic acid (PFOA) have attracted wide attention. This study focused on the PFOA photodegradation by using photocatalyst TiO2 with peroxymonosulfate (PMS) activation. Aqueous PFOA (50 mg L-1) at the pH 3 was treated by TiO2/PMS under 300 W visible light (400-770 nm) or 32 W UV light (254 nm and 185 nm). The addition of PMS induced a significant degradation of PFOA under powerful visible light compared with sole TiO2. Under visible light, 0.25 g L-1 TiO2 and 0.75 g L-1 PMS in the solution with the initial pH 3 provided optimum condition which achieved 100% PFOA removal within 8 h. Under UV light irradiation at 254 nm and 185 nm wavelength, TiO2/PMS presented excellent performance of almost 100% removal of PFOA within 1.5 h, attributed to the high UV absorbance by the photocatalyst. The intermediates analysis showed that PFOA was degraded from a long carbon chain PFOA to shorter chain intermediates in a stepwise manner. Furthermore, scavenger experiments indicated that SO4•-radicals from PMS and photogenerated holes from TiO2 played an essential role in degrading PFOA. The presence of organic compounds in real wastewater reduced the degradation efficacy of PFOA by 18-35% in visible/TiO2/PMS system. In general, TiO2/PMS could be an ideal and effective photocatalysis system for the degradation of PFOA from wastewater using either visible or UV light source.

Sulfadiazine biodegradation by Phanerochaete chrysosporium: Mechanism and degradation product identification.

Antibiotic contaminants have become a severe environmental problem in recent years and finding effective ways to deal with this issue is of great importance. In this study, Phanerochaete chrysosporium was used to degrade sulfadiazine (SDZ), which is frequently detected in the culture medium of isolates from soil and surface water systems. The results demonstrate that 10 mg L-1 SDZ can be completely degraded by P. chrysosporium under conditions of pH 5.7 and 30 °C within 6 days. The Q-Exactive-MS/MS analysis identified and confirmed several different SDZ degradation intermediates, and four proposed degradation pathways of SDZ were deduced. Moreover, enzyme activity tests revealed that manganese peroxidase and ligninolytic peroxidase played important roles in SDZ degradation. Moreover, a transcriptome analysis method was performed to explore the mechanism and pathways of SDZ degradation by P. chrysosporium in greater detail. The results of GO and KEGG analysis strongly suggest that the metabolism pathway is significantly activated and plays an important role in antibiotic degradation. Further, this is the first study to identify SDZ degradation intermediates and two main intermediates were found to be involved in possible SDZ degradation pathways. This study is also the first report results from RNA sequencing to evaluate genome-wide changes of P. chrysosporium to further explore SDZ degradation mechanism.

The occurrence, potential toxicity, and toxicity mechanism of bisphenol S, a substitute of bisphenol A: A critical review of recent progress.

Bisphenol S (BPS) has been introduced into the industry as a safer alternative to bisphenol A (BPA). The distribution of BPS has recently become an important issue worldwide, but investigations on the toxicity and mechanisms of BPS remain limited. A review of the literature reveals that BPS has widespread presence in environmental media, such as indoor dust, surface water, sediments, and sewage sludge. It has been detected in plants, paper products, some food items, and even in the human body. In addition, compared to BPA, BPS has a lower acute toxicity, similar or less endocrine disruption, similar neurotoxicity and immunotoxicity, and lower reproductive and developmental toxicity. The mechanisms underlying BPS toxicity may be related to the chemical properties of BPS in the human body, including interactions with estrogen receptors, and binding to DNA and some proteins, subsequently including exerting oxidative stress. However, further investigation on the potential risks of BPS to humans and its mechanisms of toxicity should be conducted to better understand and control the risks of such novel chemicals.

Occurrence of antibiotics in the main rivers of Shenzhen, China: Association with antibiotic resistance genes and microbial community.

The occurrence and distribution of antibiotics were investigated in surface water and sediment collected from the main rivers of Shenzhen, China. Total concentrations of 20 selected antibiotics ranged from 36.510 to 1075.687 ng L-1 (mean 244.992 ng L-1) in 31 water samples and from 28.124 to 2728.810 ng g-1 (mean 680.169 ng g-1) in 31 sediment samples. Notably, STZ and SDZ were the dominant antibiotics in both water and sediment as their higher concentrations compared with the other compounds. Furthermore, comprehensive profiling of antibiotic resistance genes (ARGs) and microbial community was performed to gain an understanding of the evolution and dissemination of ARGs in microbial communities caused by the occurrence of antibiotics in sediment samples from Maozhou River. As a result, the sul1 gene was found to be the most abundant ARG and Proteobacteria was the most abundant microorganism in all the samples (37.4-51.7%), followed by Bacteroidetes (15.3-18.4%). Statistical analysis figured out the relations among antibiotics, ARGs and microbial community. A specific conclusion could be drawn from the positive correlations among the bla_d gene, Fusobacteria, and sulfamethoxazole. It suggests that antibiotics may be positively linked to the expression of ARGs in certain bacteria, and thus high reproduction would occur within the bacterial community. Overall, the widespread distribution of ARGs underscores the need for further research on the mechanism of antibiotics influence as emerging contaminants in the environment and the associated risks to microbial community.

Tissue bioconcentration and effects of fluoxetine in zebrafish (Danio rerio) and red crucian cap (Carassius auratus) after short-term and long-term exposure.

Fluoxetion (FLU) is an antidepressant pharmaceutical most commonly detected in the aquatic environment. The present study aims to elucidate the tissue accumulation and effects of FLU using two different fish models. First, the multiple effects and the FLU levels in fish, were examined in zebrafish (Danio rerio) embryos exposed to FLU concentrations (0, 0.1, 1, 10, 100, 1000 µg/L) from 4 h post-fertilization (hpf) until 120 hpf. Exposure to FLU accelerated heart rates, postponed hatching time, and increased swimming speed of fish. A dynamic response of acetylcholinesterase (AChE) activity was also displayed in the fish. Second, a 30-day exposure experiment using red crucian carp (Carassius auratus) was performed, and it found that the concentration of FLU in fish organs increased with increasing water concentrations, but the highest FLU bioconcentration was present in the lowest FLU exposure group (0.1 µg/L). Finally, 6 days of exposure to 0.1 µg/L of FLU followed by a 6-day clearance experiment was performed with both adult zebrafish and red crucian carp. The FLU levels in different fish organs increased as exposure time increased, but they sharply declined following the 6-day clearance. Correspondingly, the changes in brain AChE activity and in antioxidant parameters in the liver were consistent with the FLU levels in the fish organs. Our study provides fundamental data on the tissue accumulation and concentration-dependent effects in fish exposed to fluoxetine.

Graphitic carbon nitride based nanocomposites for the photocatalysis of organic contaminants under visible irradiation: Progress, limitations and future directions.

Graphitic carbon nitride (g-C3N4) has drawn great attention recently because of its visible light response, suitable energy band gap, good redox ability, and metal-free nature. g-C3N4 can absorb visible light directly, therefore has better photocatalytic ability under solar irradiation and is more energy-efficient than TiO2. However, pure g-C3N4 still has the drawbacks of insufficient light absorption, small surface area and fast recombination of photogenerated electron and hole pairs. This review summarizes the recent progress in the development of g-C3N4 nanocomposites to photodegrade organic contaminants in water. Element doping especially by potassium has been reported to be an efficient method to promote the degradation efficacy. In addition, compound doping improves photodegradation performance of g-C3N4, especially Ag3PO4-g-C3N4 which can completely degrade 10mgL-1 of methyl orange under visible light irradiation in 5min, with the rate constant (k) as high as 0.236min-1. Moreover, co-doping enhances the photodegradation rate of multiple contaminants while immobilization significantly improves catalyst stability. Most of g-C3N4 composites possess high reusability enabling their practical applications in wastewater treatment. Furthermore, environmental conditions such as solution pH, reaction temperature, dissolved oxygen, and dissolved organic matter all have important effects on the photocatalytic ability of g-C3N4 photocatalyst. Future work should focus on the synthesis of innovative g-C3N4 nanocomposites for the efficient removal of organic contaminants in water and wastewater.